[1D/Python] Add solver warnings for diffusion flame solutions
[1D/Python] Add solver warnings for diffusion flame solutions

Adds warnings that check if the solution of a counterflow diffusion flame is
reasonable (not extinct, and not too close to the boundaries of the domain).

Resolves Issue 231.

Heathckliff/cantera,imitrichev/cantera,imitrichev/cantera,Heathckliff/cantera,Heathckliff/cantera,Heathckliff/cantera,imitrichev/cantera,imitrichev/cantera,imitrichev/cantera,Heathckliff/cantera,imitrichev/cantera,Heathckliff/cantera